1. Field of the Invention
The present invention relates to an ink set which includes a black ink and a color ink other than the black ink. In particular, the present invention relates to an ink set which is usable for an image-forming apparatus based on the ink-jet system.
2. Description of the Related Art
Those which are based on the use of dyes as color materials are widely used as inks to be employed for image-forming apparatuses based on the ink-jet system. However, the ink, which is based on the use of the dye, is generally inferior in water resistance. For this reason, when an image is formed, for example, on a cloth or fabric other than paper, an ink, which is based on the use of a pigment as a color material, has been hitherto used. However, when an image is formed on a cloth or the like with inks based on the use of pigments (hereinafter referred to as “pigment-based inks”, if necessary), any extreme bleeding occurs at the boundary between the black ink and the color ink other than the black ink. In order to avoid the bleeding as described above, it is also conceived that the cloth is pretreated, for example, with cellulose. However, the pretreatment requires a large amount of energy. Further, the cloth, on which an image can be formed with the pigment-based ink, is restricted.
In order to suppress the bleeding caused by pigment-based inks, for example, Japanese Patent Application Laid-open No. 2001-294788 suggests a technique in which a coagulating agent, which coagulates any one of components of a black ink, is contained in color inks of cyan, magenta, and yellow to coagulate the component contained in the black ink so that the movement of carbon black as a pigment is suppressed.
It is postulated that the bleeding of the black ink can be suppressed to some extent when the suggested technique is adopted. However, the image formation objective, which is assumed by the suggested technique, is principally paper. In the case of the cloth or the like in which gaps between fibers are large, it is impossible to suppress the bleeding equivalently to the case of the paper. Further, it is assumed that the cloth or the like is washed or laundered. However, in the case of the suggested technique, the ink is lost by the washing, and the density of the image is thinned in some cases.